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Compensatory growth is a feeding management strategy well documented in the literature. However, the molecular and histological effects on fish still require further knowledge. This study determined the biometric, morphological, and histometric changes in adults of catfish (Lophiosilurus alexandri) after chronic fasting. Sixty adults (396.6 ± 77.5 g) were tagged with microchips and distributed in two tanks (n = 30/tank), one with normal feed and the other with total food restriction for 60 d and then refed for another 15 d. Tissue and biometric samples were taken on days 20, 40, 60 and 75. Fish reared under chronic fasting presented weight loss and had significantly lower intestinal villi height, goblet cells and muscularis thickness than those fed on a control diet. In summary, a chronic food restriction protocol can change morphology and the 15-d refeeding period was not enough to reestablish the morphological parameters and weight of L. alexandri. [ABSTRACT FROM AUTHOR]

Background: There is no evidence of peptides-probiotics symbiosis as supplements in aquafeeds. Aim: To evaluate the effect of peptides and probiotics supplementation via diet on blood parameters and growth performance of juvenile P. brachypomus, an Amazonian fish, during the growth-out phase. Methods: 120 juvenile P. brachypomus (242.77 g) were placed into twelve 200-L tanks (10 fish/tank), housed in an indoor open system with constant water renovation (flow rate:1.50 L/min). The experiment used a completely randomized design with a 4×5 factorial arrangement [4 doses of supplementation (CD: commercial diet; PepD: CD+1.50% of peptides per CD weight; ProD: CD+40.00 mL of activated probiotics per kg of diet (Lactobacillus spp., Rhodopseudomonas spp., Saccharomycetes spp.); PepProD: CD+Pep+Pro); 5 sampling times (0, 2nd, 4th, 6th, 8th week); n=3]. Fish were fed twice a day at a feeding rate of 1% of body weight. At each sampling time, blood was collected and fish were measured for growth performance analysis. Data was analyzed by using two-way ANOVA and Tukey's test (p0.05). Plasma glucose decreased for all fish in the 2nd week (59.56 mg/dL); then, that level increased in fish fed with the CD (89.00 mg/dL), while fish fed with PepD, ProD and PepProD showed constant values (57.22 mg/dL). The plasma protein levels were constant in fish fed with the PepD and PepProD, (p>0.05), while fish fed with the CD and ProD showed non-constant and higher values. At the end of the trial, fish fed with the PepProD showed the highest weight gain and the lowest feed conversion rate (39.66 g; 0.97). Conclusion: It is possible to maintain the stability of plasma glucose and plasma protein by supplementing diets with peptides, but the peptides-probiotics symbiosis administrated via diet contributes to maintain the stability of plasma glucose and plasma protein and to improve the growth performance of juvenile P. brachypomus during the growth-out phase. [Open Vet J 2024; 14(6.000): 1384-1393]

Abstract Ctenoluciidae is a Neotropical freshwater fish family composed of two genera, Ctenolucius (C. beani and C. hujeta) and Boulengerella (B. cuvieri, B. lateristriga, B. lucius, B. maculata, and B. xyrekes), which present diploid number conservation of 36 chromosomes and a strong association of telomeric sequences with ribosomal DNAs. In the present study, we performed chromosomal mapping of microsatellites and transposable elements (TEs) in Boulengerella species and Ctenolucius hujeta. We aim to understand how those sequences are distributed in these organisms’ genomes and their influence on the chromosomal evolution of the group. Our results indicate that repetitive sequences may had an active role in the karyotypic diversification of this family, especially in the formation of chromosomal hotspots that are traceable in the diversification processes of Ctenoluciidae karyotypes. We demonstrate that (GATA)n sequences also accumulate in the secondary constriction formed by the 18 S rDNA site, which shows consistent size heteromorphism between males and females in all Boulengerella species, suggesting an initial process of sex chromosome differentiation.

Hypostomus is the most species-rich genus within the family Loricariidae and is widely distributed throughout the Neotropical region. Nonetheless, the diversity and distribution of these species have still large knowledge gaps. This scenario is more significant in some regions, such as the northeast of Brazil. In this region, the first species of the genus, H. pusarum , was described in the Northeast Caatinga and Costal Drainages ecoregion. Six congeners were subsequently described in the same ecoregion, all sharing the same colour pattern making them difficult to distinguish. All of them are collectively referred to as the H. pusarum complex. The present work seeks to clarify the diversity that constitutes the H. pusarum complex through an integrative study using molecular and morphological data. The results indicate that H. carvalhoi , H. jaguribensis , H. nudiventris , H. papariae , and H. salgadae are all junior synonyms of H. pusarum. However, one of the morphotypes that occurs in the Parnaíba River is a new species that differs from the others by the absence of a developed medial buccal papilla and the presence of a pre-anal plate. The data provided here highlight the importance of integrative taxonomy for assessing diversity in complex and diverse groups in the Neotropics. [ABSTRACT FROM AUTHOR]

Astyanax caucanus is an endemic fish species to the Magdalena-Cauca basin in Colombia. It is considered a Least Concern species by the International Union for Conservation of Nature, and currently, it is not a fishery resource. Its fertilized eggs may drift up to 4–5 days before hatching and can be carried up to 340 km given the water velocity of the river. Although A. caucanus is listed as short -migratory species (< 50 km), this study hypothesized that it exhibits gene flow along the middle and lower section of the Cauca River due to the great potential for larval dispersal. To test this hypothesis, we developed a set of species-specific microsatellite primers suitable for population genetic studies. Genetic structure analyses with 193 samples evidenced two genetic stocks that coexist, comigrate, and exhibit gene flow along the study area. Both stocks show high genetic diversity indices (Na and HE) and effective population sizes (Ne > 1000), but also show evidence of bottlenecked populations and high values of the inbreeding coefficient (FIS). Finally, these results are useful to understand the effects of other anthropic activities, besides fishing pressure on population bottlenecks found for other fish species cohabiting the area. [ABSTRACT FROM AUTHOR]

The early development of the freshwater fish Rhytiodus microlepis is characterized by the description of external morphological, meristic, and morphometric changes, as well as the growth patterns, thereby establishing a reference for the identification of its larvae and juveniles. Specimens were collected from the Amazon river channel and floodplain. Ninety‐seven individuals were analysed with standard length varying between 4.31 and 79.23 mm. Rhytiodus microlepis larvae are altricial, with an elongated and fusiform body, anal opening reaching the middle region of the body, and simple nostrils becoming double and tubular during development. The pigments vary from one to two chromatophores in the dorsal region of the head in pre‐flexion and flexion, but later the pigmentation pattern intensifies, transverse bands appear along the body, and a conspicuous spot appears in the basal region of the caudal fin. The total number of myomeres ranges from 49 to 50. During the transition from larval (post‐flexion) to the juvenile periods, the most significant anatomical changes occur, such as the presence of all fins and increased body pigmentation. Integrated myomere count and pigmentation pattern are effective for the correct identification of the initial life stages of R. microlepis from the Amazon basin. Our results expand the knowledge about the early life history of Neotropical freshwater fish species. [ABSTRACT FROM AUTHOR]

This study explored ultrasonography, exfoliative cytology, and celiotomy as methods for sex determination in Pimelodus maculatus, a species included in fish-stocking programs aimed at conserving and recovering populations affected by hydroelectric power plant activity. Three-year-old fish (n=40), with an average weight of 81.3 ± 16.6 g and average length of 18.9 ± 1.2 cm, were examined in series, according to the degree of invasiveness of these techniques. Ultrasonography showed the ovaries as structures with smooth and defined margins and hypoechoic and homogeneous parenchyma, while the testes were isoechoic to the adjacent structures. Cytology of the urogenital region revealed cellular elements with an accuracy rate of 80 % for females and zero for males. In celiotomy, 100 % accuracy in sex determination was achieved, with 100 % survival after 30 days, indicating rapid recovery. This study provides new insights into the applicability of methodologies for determining the sex of P. maculatus, thereby contributing to the management and conservation of this species.

Sex development is a multi-step process involving determination, differentiation, and maintenance of the gonads, which culminates in producing fertile sperm and eggs. In teleosts, candidate genes mastering this process can be thermosensitive before or just at the beginning of differentiation, the sensitive period in fish. The knowledge of these mechanisms may be useful for the production of monosex populations in aquaculture. Here we investigated the influence of temperature on survival, growth, expression profiles of genes involved in early sexual development, and sex ratio. 5-day-old (undifferentiated) larvae were reared at 26, 28 and 31 °C for 90 days, and expression of genes involved in testis- (wt1b and ar) and ovary-determining (amh and foxl2) pathways, and vasa, were analysed four times from 20 to 90 days post-hatching, and the resulting sex ratios were estimated. Only foxl2 showed a thermosensitive transcription at 20 dph, decreasing at the highest temperature. None of the male-bias genes were regulated by temperature. Still, both wt1b and ar were upregulated in some individuals long after sex differentiation, suggesting the importance of testis-skewed genes not only at testis establishment but also at later stages. The sex ratio was not affected by temperature. Our study also revealed an unusual vasa expression profile before and after gonadal differentiation; in some fish increasing expression values were recorded while others presented low vasa expression even after differentiation. Our results support a strict genetic control in the sex determination of tambaqui, despite thermosensitivity of some genes involved in its sexual development. [ABSTRACT FROM AUTHOR]

The lectotype specimen of Bryconamericus rubropictus (Berg) and its designation have remained imprecisely documented since its publication. The lack of a photograph or an unambiguous illustration, correct size, inaccurate labelling, and proper specimen separation has led to an uncertainty about the identity and nomenclatural status of the lectotype. We recovered and provided detailed morphological data on the specimen that must be recognised as the lectotype. This contribution brings stability and clarity on the nomenclatural status of the species and its type material. [ABSTRACT FROM AUTHOR]

Abstract Pseudanos is a fish genus with cis-Andean distribution in South America. Pseudanos trimaculatus is originally known from the Amazon and Orinoco basins. Three decades ago, a few specimens collected in the Río de la Plata basin were identified as P. trimaculatus, what remained to be confirmed and understood. The aim of this contribution is to analyze these specimens. Consequently, the morphological variation of P. trimaculatus is discussed and updated. Morphometric and meristic data were taken from the specimens and compared with those of the type and non-type specimens of the species. Multivariate analyses of the size-corrected measurements were used to explore the morphological variation. Size-corrected PCA revealed that the specimens collected in the Río de la Plata basin nested with the remaining specimens, being slightly closer to those from the Guaporé, Napo and Uatumã rivers. Measurements such as caudal peduncle depth, body depth, and body width affected more heavily the first components. Cluster analysis did not show well-defined groups based on the hydrogeographic basins. The studied specimens from the Río de la Plata basin are herein confirmed as conspecific with P. trimaculatus. The species is added to the list of fish species shared between the Amazon and Río de la Plata basins.

ABSTRACT: Phractocephalus hemioliopterus, Hemisorubim platyrhynchos, and Zungaro zungaro are native of South American rivers whose population is being threatened by the damming of rivers to build hydroelectric dams, fishing pressure and environmental degradation. Basic information on these species’ reproductive characteristics is necessary to enable production in captivity. The aim of this study was to present descriptive data regarding the sperm parameters of these three species maintained in captivity, the correlations between these parameters, and relevant factors, and how these issues can affect sperm quality. Sperm was collected and diluted in Beltsville Thawing Solution after hormonal induction with carp pituitary extract. The evaluated parameters for Hemisorubim platyrhynchos, Phractocephalus hemioliopterus, and Zungaro zungaro were, respectively: Sperm concentration (×109) was 3.00, 1.77, and 1.40 sperm mL−1; Sperm total length was 93.2, 91.4, and 79.4 μm; Motility rate was 71.8, 73.5, and 61.7%; Normal sperm was 35.5, 38.8, and 30.2%. Describing sperm characteristics is extremely important for the artificial reproduction of fish in captivity, contributing to the knowledge on the reproductive biology of the species. In the present study, we discuss these issues to build the knowledge necessary for sperm characterization of these little-studied species. Our results suggest that the morphological abnormalities can affect motility and sperm movement kinetics.

Tetragonopterus is a taxonomically complex genus in Characidae, being currently represented by nine species according to integrative approaches. One of them, T. franciscoensis was recently validated in rivers from northeastern Brazil. Even though molecular and morphological data have been collected in Tetragonopterus, the cytogenetic analyses in this group are scarce despite of the role of chromosomal variation in speciation. Herein, we present the first detailed karyotypic study in T. franciscoensis along with a comparative analysis with published cytogenetic data in characin fish. All specimens shared 2n=52 distributed in 12 metacentric (m), 12 submetacentric (sm), and 28 subtelocentric/acrocentric (st/a) chromosomes for both sexes as well as single nucleolus organizer regions on short arms of pair 8 and several GC-rich sites. The mapping of telomeric sequences (TTAGGG)n revealed no telomeric interstitial signals. While subtle cytogenetic differences were observed between samples from northeastern basins in Brazil, corroborating a recent genetic divergence, distinct karyotypes were detected in relation to congeneric taxa from other Brazilian regions. Therefore, the origin of large biarmed pairs in species with low 2n values should be related to occurrence of centric fusions.

We report the results of a taxonomic revision of the species of Bryconamericus from the Amazon River Basin of Peru, Ecuador, Bolivia and the Pacific coastal rivers of Peru. Based on morphological analyses, four valid species are recognized: B. bolivianus Pearson 1924, B. osgoodi Eigenmann & Allen 1942, B. pachacuti Eigenmann 1927 and B. phoenicopterus (Cope 1872). Three new species are described: B. lambayequensis sp. n. from the Cañariaco River, Pacific coast, Peru and two from the Amazon River Basin: B. abalio sp. n. from the Ucayali River drainage, Peru, and B. parapetiensis sp. n. from Itenez/Parapeti, Amazonia, Bolivia. Two species are synonymized and one was recently assigned to another genus: Bryconamericus alfredae is considered a junior synonym of Acrobrycon ipanquianus; Bryconamericus grosvenori is a junior synonym of B. bolivianus. A taxonomic key to these species of Bryconamericus and comments on the conservation status of the Amazonian and Pacific coast freshwater ichthyofauna are also included.

We report the results of a taxonomic revision of the species of Bryconamericus from the Amazon River Basin of Peru, Ecuador, Bolivia and the Pacific coastal rivers of Peru. Based on morphological analyses, four valid species are recognized: B. bolivianus Pearson 1924, B. osgoodi Eigenmann & Allen 1942, B. pachacuti Eigenmann 1927 and B. phoenicopterus (Cope 1872). Three new species are described: B. lambayequensis sp. n. from the Cañariaco River, Pacific coast, Peru and two from the Amazon River Basin: B. abalio sp. n. from the Ucayali River drainage, Peru, and B. parapetiensis sp. n. from Itenez/Parapeti, Amazonia, Bolivia. Two species are synonymized and one was recently assigned to another genus: Bryconamericus alfredae is considered a junior synonym of Acrobrycon ipanquianus; Bryconamericus grosvenori is a junior synonym of B. bolivianus. A taxonomic key to these species of Bryconamericus and comments on the conservation status of the Amazonian and Pacific coast freshwater ichthyofauna are also included. [ABSTRACT FROM AUTHOR]

Here, we report the first observation of a leucistic specimen in the Rock catfish, Rhamdia laticauda in the Northeast of Oaxaca, Mexico. We caught the specimen by electric fishing and then photographed during an ichthyological survey carried out in the Tehuacán-Cuicatlán Biosphere Reserve in the Xiquila River of the upper Papaloapan River basin. The live catfish showed a lack of pigment in the skin, white spots, and normal eye color. This information contributes to the knowledge about intraspecific variability and natural history of R. laticauda. We discuss the potential causes of this color anomaly. [ABSTRACT FROM AUTHOR]

The black soldier fly (BSF, Hermetia illucens) is a prominent insect species and a novel alternative ingredient for aquafeeds. This study aimed to evaluate the replacement of commercial feed with fresh whole black soldier fly larvae (BSFL) for Colossoma macropomum. Juvenile tambaqui (115.2 ± 0.9 g/fish) were stocked in 800 L tanks (11 fish/tank) operating as a recirculating system. The dietary treatments consisted of whole larvae only (BSFL), 50:50 BSFL: commercial feed (BSFL: CF), or only commercial feed (CF), and the fish were fed to apparent satiation for 120 days. At the end of the feeding trial, fish were group weighed, and blood and muscle were collected for hematological and sensorial evaluations. Fish fed BSFL:CF presented with similar growth performance and carcass yield to tambaqui that were fed only CF. The high fat content of the larvae contributed to the highest values for the viscerosomatic index (7.01%; 6.56%), plasmatic triglycerides (312.1 mg/dL; 295.1 mg/dL), and cholesterol (120.6 mg/dL; 119.1 mg/dL) in the fish provided with BSFL or BSFL:CF, respectively. However, a better acceptance in the fillet sensory analysis was observed for these fillets than for the fillets from the CF group. Feeding tambaqui with BSFL:CF did not compromise the production performance and may have improved the acceptance of their fillets.

Construction of dams for hydropower in Andean rivers of Colombia is increasing loss of species of the region. Fish species that persist in these artificial ecosystems are those which find favorable the new conditions for their recruitment. Because feeding is one of the fish life strategies that influence their persistence in reservoirs, we analyzed the stomach contents of the species present in two cascade reservoirs in the Magdalena river basin. The objectives were to describe the diet, to determine their feeding strategies and to evaluate if the rainy season or spatial distribution affects the diet of the fish species. Our results indicate that the fish species Brycon henni and Astyanax microlepis that feed on a wide range of resources that the system offers and adopt a generalist strategy. Also, opportunistic species such as Roeboides dayi and Hoplosternum magdalenae occupied these environments. Climatic seasonality does not influence the feeding habits of the fish species inhabiting the study reservoirs. Knowledge of the feeding habits of fish species is a priority for strengthening the environmental management of aquatic resources of the Andes.

We studied the reproductive strategy, sexual system and growth of dientudo paraguayo Acestrorhynchus pantaneiro. After 2 years of monitoring in shallow areas of a floodplain lake from the lower Paraná basin (Argentina), it was evidenced that water temperature modulated gonadal maturation, but it was the river water level the synchronising stimulus that triggered spawning. This species exhibited a single annual breeding period from October to January, with most spawning activity in November. According to the von Bertalanffy growth curve, fish would reach autumn to winter months with LS of ~120 mm, already mature males. The first mature females were found at LS of 210 mm, becoming sexually mature between the second and third breeding seasons. This is the first integrative study that includes the body‐length frequency distribution and sex differential size at first maturity and growth, and reports the presence of intersex gonads questioning its sexual pattern from gonochoristic to sequential hermaphrodite species. The sexual pattern, the multiple spawning behaviour and a medium to high absolute fecundity support the opportunistic and invasive behavior observed in previous contributions for this characiform species. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of live prey concentration (nauplii of Artemia sp.), water salinity, and weaning age on survival, growth, and stress resistance rate (Rs) of Piaractus brachypomus under larviculture in a recirculating aquaculture system (RAS). Larvae aged 6 days post-hatching (1.64 ± 0.11 mg) were distributed in 28-L tanks (five larvae L−1), in two RASs. The experiment was carried in a 2 × 2 × 2 factorial arrangement, as follows: two feeding strategies (sudden transition from live food to commercial food after 10 (FT10) and 20 (FT20) days of larviculture with Artemia); two daily initial prey concentrations (P350 = 350 and P700 = 700 nauplii larva−1, these being increased every 5 days); and two water salinities (S0 = fresh water and S2 = 2 g of salt L−1). Weight (W), total length (TL), and daily specific growth rate (SGR) were evaluated after 10, 20, 30, and 40 days of larviculture. After 40 days of larviculture, survival was evaluated and a test of air exposure was performed to determine stress resistance rate (Rs). Noteworthy results during this period are the lowest specific daily growth rate (SGR) after weaning for FT10 and the best growth results for S2 and P700. After 40 days, weight (W) and total length (TL) showed effects of P, FT, and S with higher values for P700, FT20, and S2 (P < 0.05). The interaction P × FT × S also had effects on survival and Rs at the end of the experiment, with higher survival and Rs for P700FT20S2 (P < 0.05). Larviculture of P. brachypomus in RAS, in association with the three managements—live prey concentration P700, salinity S2, and age at feed transition FT20—promotes maximization of survival, growth, and stress resistance rate of the animals. The larviculture of P. brachypomus in RAS must be carried out with an initial concentration of live prey of 700 nauplii larva−1, at a salinity of 2 g of salt L−1 and with the feeding transition starting in 20 days of larviculture, for maximization intensive larviculture of this species. [ABSTRACT FROM AUTHOR]

Fish viscera can be an important source of protein and energy for aquafeed, and its use contributes to circular aquaculture. The aim of this study was to produce acid and fermented silage from fish viscera to determine their nutritional value and the apparent digestibility coefficient of nutrients and energy for juvenile tambaqui (Colossoma macropomum). An acid silage and three fermented silages with different sources of carbohydrates (molasses, wheat bran, and cassava waste) were produced with 0.25% sorbic acid as an antifungal in the formulation. Silages presented an average of 55% dry matter, 62.9% lipids, and 12% crude protein. Leucine and lysine predominated as essential amino acids in the acid silage and fermented silages. Fish viscera silages presented EPA and DHA content from 5.4 to 17.8 and 1.7 to 8.9 mg.g−1 of lipids, respectively. The apparent digestibility coefficient (ADC) (indirect method) was above 82% for gross energy for all the formulations. The ADCs for protein were similar for the fermented silages, with a maximum 92% level for the fermented wheat bran silage. The bioconversion of fish viscera into silage makes it an energy ingredient for aquafeed that is well digested by tambaqui juveniles. [ABSTRACT FROM AUTHOR]

The peace process in Colombia allowed biodiversity experts to visit unexplored regions in the tropical Andes mountains. The diversity of fish species and characteristics of the aquatic environments (creeks, streams, and river channels) in which they live were determined by means of the Bio Anorí expedition. During the expedition, we evidenced the presence of alluvial mining activity, and we contrasted the environmental characteristics of the sites without disturbances with those where there was mining activity. A total of 478 specimens were captured, representing 22 endemic species of the region. The dominant species (Brycon henni, Chaetostoma aff. brevilabiatum, Creagrutus affinis) were distributed in the three environments, while the less abundant species (e.g., Leptoancistrus or Characidium) were captured in a particular environment. The number of species captured in each aquatic environment was representative and adjusted to the values expected to be obtained. Stream environments harbored a higher diversity of fish. A representative species inventory was inferred; however, this analysis suggested that it is possible to capture more species in the aquatic environments evaluated. The composition of assemblages was similar among aquatic environments; although, differences were observed between creeks and rivers. Stream environments connected creeks and river assemblages. In terms of environmental characteristics, the evaluated streams and creeks were cold, more transparent, and highly oxygenated; the opposite occurred in the rivers, which were less oxygenated, more turbid, and warmer. Canonical correspondence analysis suggested that species composition was influenced by the physicochemical conditions of the water. This study provides information associated with fish distribution in a region of the Colombian Andes that was under an armed conflict for more than five decades. In addition, it allowed us to observe habitat transformations because of alluvial mining activity. Finally, it is essential to continue exploring remote areas to know their preservation status and apply conservation measures.

Abstract Few studies have focused on non-troglomorphic fishes occurring in Brazilian caves, especially those in the Caatinga region. The present study is the first survey of fishes from karstic areas of the Jandaíra Formation in Rio Grande do Norte State, northeastern Brazil. This region is characterized by a high concentration of caves and a rich subterranean biodiversity, especially of troglobitic invertebrates, but remains considered a gap on the knowledge of the subterranean ichthyofauna in Brazil. Four field expeditions were carried out covering two dry and two rainy seasons, in 2018 and 2019, in 23 localities in small river basins along the western part of the Jandaíra Formation. A total of 829 fish specimens, none of them troglomorphic, was captured and identified as belonging to 25 species of 12 families and five orders. Amongst them, four species are endemic of the Mid-Northeastern Caatinga ecoregion, and two non-native species were recorded. Habitats were classified into three categories: superficial, associated to cave, and cave. Although no troglomorphic fish species was found in this study, we recorded 64.1% of the Apodi-Mossoró river ichthyofauna occurring in caves or associated to caves, corroborating the hypothesis that part of the ichthyofauna exploits these environments as a refuge during the dry season. In addition, we suggest conservation policies for the maintenance of subterranean and aquatic semiarid ecosystems in the Jandaira formation, which is currently under threat due to anthropogenic activities, such as mining and deforestation.

The initial development of the red‐bellied pacu Piaractus brachypomus is described using morphological, meristic and morphometric characteristics. A total of 127 individuals were analysed (47 in the yolk‐sac, 35 in pre‐flexion, five in flexion, 20 in post‐flexion and 20 in juvenile) with standard length varying between 2.92 and 48.61 mm. The larvae are born poorly developed and have a discoidal yolk at ~6.33 mm standard length. During early ontogeny, the mouth passes from terminal to subterminal and the anal opening reaches the vertical line over the midline region of the body. There are changes in body shape from long and moderate to deep, head length from small to large, and eye diameter from moderate to large. Dendritic chromatophores were present in the ventral, dorsal and upper part of the swim bladder in the early larval stages. Rounded spots are evident all over the body in juveniles. The total number of myomeres ranges from 39 to 41 (20–23 pre‐anal, 17–20 post‐anal). Through the morphometric relationships, it was evidenced that the greatest changes during the initial ontogeny of P. brachypomus occur in the transition from the post‐flexion stage to the juvenile period, indicating changes in behaviour, foraging and physiology. [ABSTRACT FROM AUTHOR]

The habitat fragmentation caused by reservoir construction in different aquatic systems in the Magdalena River basin is a latent threat to the diversity of fishes and aquatic environments in the Andean region of Colombia. Contributing to the knowledge about how fish assemblages are formed in these scenarios is fundamental for the management and decision-making on the aquatic resources of the basin. In this communication, we describe the results of a fish characterization in the area of influence of the Piedras Blancas reservoir, a high Andean reservoir built for hydroelectric power generation. Only three species of fish that make up the evaluated assemblage were captured, and two of them, Cyprinus carpio and Xiphophorus maculatus, are not native to the basin. Possibly, with a greater sampling effort, more species can be found. The native species Hemibrycon sp. is distributed mainly in a creek, while in the reservoir, the introduced species dominate. The environmental variables were in optimal ranges for the development of life in the evaluated environments. It is important to advance the knowledge about the distribution of the introduced and native species in the basin to generate recommendations that contribute to the management of these species in the aquatic systems of Colombian Andes. [ABSTRACT FROM AUTHOR]

The black soldier fly (BSF, Hermetia illucens) is a prominent insect species and a novel alternative ingredient for aquafeeds. This study aimed to evaluate the replacement of commercial feed with fresh whole black soldier fly larvae (BSFL) for Colossoma macropomum. Juvenile tambaqui (115.2 ± 0.9 g/fish) were stocked in 800 L tanks (11 fish/tank) operating as a recirculating system. The dietary treatments consisted of whole larvae only (BSFL), 50:50 BSFL: commercial feed (BSFL: CF), or only commercial feed (CF), and the fish were fed to apparent satiation for 120 days. At the end of the feeding trial, fish were group weighed, and blood and muscle were collected for hematological and sensorial evaluations. Fish fed BSFL:CF presented with similar growth performance and carcass yield to tambaqui that were fed only CF. The high fat content of the larvae contributed to the highest values for the viscerosomatic index (7.01%; 6.56%), plasmatic triglycerides (312.1 mg/dL; 295.1 mg/dL), and cholesterol (120.6 mg/dL; 119.1 mg/dL) in the fish provided with BSFL or BSFL:CF, respectively. However, a better acceptance in the fillet sensory analysis was observed for these fillets than for the fillets from the CF group. Feeding tambaqui with BSFL:CF did not compromise the production performance and may have improved the acceptance of their fillets. [ABSTRACT FROM AUTHOR]

The São Francisco River (SFR), one of the main Brazilian rivers, has suffered cumulative anthropogenic impacts, leading to ever-decreasing fish stocks and environmental, economic, and social consequences. Rhinelepis aspera and Prochilodus argenteus are medium-sized, bottom-feeding, and rheophilic fishes from the SFR that suffer from these actions. Both species are targeted for spawning and restocking operations due to their relevance in artisanal fisheries, commercial activities, and conservation concerns. Using high-throughput sequencing of the 16S rRNA gene, we characterized the microbiome present in the gills and guts of these species recruited from an impacted SFR region and hatchery tanks (HT). Our results showed that bacterial diversity from the gill and gut at the genera level in both fish species from HT is 87% smaller than in species from the SFR. Furthermore, only 15 and 29% of bacterial genera are shared between gills and guts in R. aspera and P. argenteus from SFR, respectively, showing an intimate relationship between functional differences in organs. In both species from SFR, pathogenic, xenobiont-degrading, and cyanotoxin-producer bacterial genera were found, indicating the critical pollution scenario in which the river finds itself. This study allowed us to conclude that the conditions imposed on fish in the HT act as important modulators of microbial diversity in the analyzed tissues. It also raises questions regarding the effects of these conditions on hatchery spawn fish and their suitability for restocking activities, aggravated by the narrow genetic diversity associated with such freshwater systems. [ABSTRACT FROM AUTHOR]

Abstract Tambaqui or cachama (Colossoma macropomum) is one of the most important neotropical freshwater fish used for aquaculture in South America, and its production is concentrated at low latitudes (close to the Equator, 0°), where the water temperature is warm. Therefore, understanding how selection shapes genetic variations and structure in farmed populations is of paramount importance in evolutionary biology. High‐throughput sequencing to generate genome‐wide data for fish species allows for elucidating the genomic basis of adaptation to local or farmed conditions and uncovering genes that control the phenotypes of interest. The present study aimed to detect genomic selection signatures and analyze the genetic variability in farmed populations of tambaqui in South America using single‐nucleotide polymorphism (SNP) markers obtained with double‐digest restriction site‐associated DNA sequencing. Initially, 199 samples of tambaqui farmed populations from different locations (located in Brazil, Colombia, and Peru), a wild population (Amazon River, Brazil), and the base population of a breeding program (Aquaculture Center, CAUNESP, Jaboticabal, SP, Brazil) were genotyped. Observed and expected heterozygosity was 0.231–0.350 and 0.288–0.360, respectively. Significant genetic differentiation was observed using global FST analyses of SNP loci (FST = 0.064, p

ABSTRACT: Here we show that selected nutritional feed additives reduce the adverse effects of transport stress on the immune system and hematology of tambaqui. We formulated a control diet to contain normal dietary levels of vitamin E (21.6 mg/ kg diet) and C (143 mg/kg), then we added supra levels of these vitamins (vit E – 264 mg/kg and vit C – 1000 mg/kg) to a second diet. Finally, a third diet was produced to contain similar levels of vitamins from diet 2 with 0.1% beta-glucan supplementation. Four hundred thirty-two tambaquis (20.91 g ± 0.27 g) were randomly assigned to 12 aquaria and fed the diets for 15 days; then, all fish were transported for five h and then returned to the aquaria. Blood samples were collected before and after the transport and at the end of the trial (60 days). Transportation significantly increased blood glucose that returned to baseline levels at the end of the trial. However, cortisol seemed to be unresponsive to the stress. Surprisingly, the stress significantly increased the immunoglobulin level after transport. Additionally, the transport markedly reduced the red blood cell count and leukocyte and lymphocytes counts while increasing the control group's neutrophil number. These effects lasted until the end of the trial in the control group. Supra levels of the vitamins and glucan supplementation prevented the decrease in red blood cell and leukocyte count after the stress. Additionally, beta-glucan supplementation induced lower cortisol levels in all the sampling points. However, the effect on the immune parameters was limited, increasing only the lysozyme activity and serum protein levels in the beta-glucan supplemented group and the group fed only the supra levels of vitamins, respectively. In sum, our results indicated that transport for five h induced a limited effect on stress biomarkers. The use of supra levels of antioxidant vitamins alone or in combination with beta-glucan could restore or prevent the adverse effects of stress on hematology and the immune system.

The São Francisco River (SFR), one of the main Brazilian rivers, has suffered cumulative anthropogenic impacts, leading to ever-decreasing fish stocks and environmental, economic, and social consequences. Rhinelepis aspera and Prochilodus argenteus are medium-sized, bottom-feeding, and rheophilic fishes from the SFR that suffer from these actions. Both species are targeted for spawning and restocking operations due to their relevance in artisanal fisheries, commercial activities, and conservation concerns. Using high-throughput sequencing of the 16S rRNA gene, we characterized the microbiome present in the gills and guts of these species recruited from an impacted SFR region and hatchery tanks (HT). Our results showed that bacterial diversity from the gill and gut at the genera level in both fish species from HT is 87% smaller than in species from the SFR. Furthermore, only 15 and 29% of bacterial genera are shared between gills and guts in R. aspera and P. argenteus from SFR, respectively, showing an intimate relationship between functional differences in organs. In both species from SFR, pathogenic, xenobiont-degrading, and cyanotoxin-producer bacterial genera were found, indicating the critical pollution scenario in which the river finds itself. This study allowed us to conclude that the conditions imposed on fish in the HT act as important modulators of microbial diversity in the analyzed tissues. It also raises questions regarding the effects of these conditions on hatchery spawn fish and their suitability for restocking activities, aggravated by the narrow genetic diversity associated with such freshwater systems.

Aim of study: To evaluate which vegetable lipid source promotes better growth performance, whole-body composition and fatty acid profile for juvenile giant trahira (Hoplias lacerdae). Area of study: Fish Nutrition Laboratory of the University of Viçosa (UFV), MG, Brazil. Material and methods: A 50-day feed trial with four treatments, consisting of diets containing different vegetable lipid sources (canola, linseed, soybean or olive oil), was conducted with juveniles of 4.76 ± 0.50 cm and 1.97 ± 0.20 g. Main results: There were no effects of vegetable lipid sources on growth performance. Fish fed diets containing canola oil had higher body lipid deposition and fish fed with linseed oil had lower body lipid content (up to -19.29%) than fish from other treatments. Fish fed canola oil showed lower proportions of saturated fatty acids (up to -11.27%) in the body. Fish fed diets containing soybean oil and linseed oil showed the highest percentages of linoleic and α-linolenic fatty acids, respectively. Fish fed diets containing soybean and linseed oils also had higher total polyunsaturated fatty acids content (up to +81.14%). Fish fed diets containing linseed oil had lower content of monounsaturated fatty acids (up to -58.59%) and higher content of docosahexaenoic (up to +175%) and eicosapentaenoic (not detectable to detectable) acids. Research highlights: Juveniles of giant thraira can alter the whole-body fatty acid profile due to their ability to desaturate and elongate the n3 and n6 series fatty acids. Linseed oil was identified as lipid source for this fish species.

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In the Magdalena River basin, fish rescue activities are an environmental management measure used to reduce fish mortality in the area near the reservoirs. When the opening and subsequent closing of the spillway gates is carried out as a result of the operation of the Porce III hydroelectric plant, downstream of the dam temporary aquatic habitats are created in the form of minor pools in the bedrock, where fish entrapment occurs. The objective of rescue activities is to relocate them to the main channel of the river, to reduce mortality. Between the years 2013 to 2020, a total of 4927 individuals were captured, representing 28 species, 12 families and five orders. We relocated 4704 individuals back to the Porce river, being the species of the genera Chaetostoma, Andinoacara, Astyanax and Rhamdia the highest capture. Potamodromous species of the family Prochilodontidae were also captured, their presence close to the dam possibly being due to the migrations they make to carry out their reproduction. These rescue and relocation actions resulting from the operation of hydroelectric plants should be replicated in the basin, as a strategy to mitigate the environmental impacts caused by habitat fragmentation. [ABSTRACT FROM AUTHOR]

Drainage rearrangements, either headwater captures or coastal paleodrainages formed when sea level was low, are often invoked to explain connectivity and isolation among fish populations. Unravelling these events is crucial for understanding the evolutionary processes that have shaped the genetic diversity and differentiation in freshwater fishes, which is especially relevant in regions with high endemism and species richness.Here, we analyse mitochondrial (cytochrome c oxidase subunit I) and genomic (restriction site‐associated DNA) data to test the putative effects of the current configuration of basins and historical drainage rearrangements on the genetic structuring of a characid fish (Nematocharax) endemic to a largely overlooked Neotropical freshwater ecoregion—the North‐eastern Mata Atlantica. Bathymetric and geomorphological data were also used to generate hypotheses for two potential routes of dispersal (headwater captures and coastal paleodrainages).We found that the divergence between lineages from the highlands of the Brazilian shield and the lowlands occurred during the Mio‐Pliocene (i.e., divergence between Nematocharax varii and Nematocharax venustus), followed by divergence events within N. venustus in lowland basins during the Pleistocene. The general distribution of genetic variation in N. venustus seems to reflect the current configuration of basins, suggesting long‐term isolation, but a subset of the inferred drainage rearrangements have facilitated movement among these catchments, which is supported by both mitochondrial DNA and genomic data.Our results suggest that the North‐eastern Mata Atlantica river basins have had their own independent histories, except for some past temporary connections that allowed dispersal events and multiple independent colonisation of basins, as seen in the Contas and Cachoeira river systems.Estimating when and where connections between river basins may have occurred is fundamental to understand the role of different historical processes structuring divergence in freshwater fish species. [ABSTRACT FROM AUTHOR]

Copyright of Caldasia is the property of Universidad Nacional de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Caldasia is the property of Universidad Nacional de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Aim We characterize the diet and trophic guild to the fish community in a protected area to contribute information about the trophic ecology. Methods The collection was carried out at three sampling points, in 2017 and 2018, with the help of gill nets. The collected specimens were euthanized in a 0.5% benzocaine solution. In the laboratory, all specimens' stomachs were removed, fixed in a 4% formalin solution, and preserved in 70% alcohol. Stomach contents were examined, and the food items were identified to the lowest possible taxonomic level. Food items were quantified according to the volumetric method. The characterization of the diet was presented through the percentage volume of each food item consumed. To determination of the trophic guild of each species, the predominance of a type of food resource (> 51% of the total volume) in the population's diet was considered. Results The species' diets were distributed in 16 food items (predominance of decapods, fish fragments, terrestrial insects, and aquatic plants), and four trophic guilds were observed (carcinophage, piscivore, terrestrial insectivore, and herbivore). Furthermore, there was the occurrence of microplastic in the diet of three species. Conclusions the fish community evaluated here demonstrates the wide range of resources that can make up the fish diet and demonstrates the different trophic guilds that can be observed in a protected area. As it is a conservation unit, knowing the diet and trophic guilds that make up the fish community can contribute to understanding the dynamics of food chains, the structure of the community, and the functioning of the ecosystem. Thus, this work can contribute information about the biology of the species evaluated for future work and conservation programs.

Outside of scientific circles, climate change is a hotly debated topic due to all its consequences. Changes in the temperature can affect aquatic organisms and it is important to understand and to detect earlier signals. This study aimed to analyze how a Neotropical fish species responds to temperature increases, using proteomic analysis as a tool. For this, fish of the species Rhamdia quelen , male and female, were exposed to two temperatures: 25 °C and 30 °C. After 96 h, the animals were anesthetized, euthanized and the liver was collected for proteomic analysis. Using freely available online software and databases (e.g. MetaboAnalyst, Gene Ontology and UniProt), we define the altered proteins in both sexes: 42 in females and 62 in males. Data are available via ProteomeXchange with identifier PXD046475. Differences between the two temperatures were observed mainly in the amino acid metabolic pathways. The cellular process and the immune response was altered, indicating that effects at lower levels of biological organization could serve as a predictor of higher-level effects when temperature rise affects wildlife populations. Thus, we conclude that the increase in temperature is capable of altering important cellular and physiological processes in R. quelen fish, with this response being different for males and females. [Display omitted] • Temperature rise changes catfish hepatic protein content. • Proteins related at cellular process and structure were affected with temperature rise. • Temperature rise can increase the abundance of immune system proteins. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the comparative growth performance, carcass yield, and the proximate composition of the muscle between male and female Arapaima gigas (pirarucu) during the fattening phase. Juvenile pirarucu (n = 114; 1126 ± 219 g; 55 ± 3 cm) were kept in 120 m2 brick tanks at a stocking density of 1.55 g m-2. Fish were raised under the same management conditions during 427 days and biometrics were performed monthly to evaluate the growth performance. Fish (n = 15 per collection day) were sampled at 91, 187, 273, 341 and 427 days to evaluate the carcass yield, proximate composition of the muscle and to determine its gender via histological analysis of the gonads. Data were analyzed using a multivariate statistical method. Growth performance, carcass yield and proximate composition of the muscle were similar between genders up to 427 days of rearing. The coefficients of variation in total weight and length that express the batch heterogeneity were higher for females throughout practically the whole experimental period. This was probably due to the dominance behavior between female fish, which also justifies why some females reached larger sizes at the end of the experiment. The yields for the fillet, abdominal muscle and loin were greater at 273 days compared to other sampling events, regardless of gender. Partial harvesting of pirarucu during the fattening phase can therefore be a management strategy for slaughtering fish with a higher meat yield. • The male and female pirarucu showed similar growth performance and carcass yield. • Female pirarucu showed greater size heterogeneity during the fattening phase. • Partial harvest during the fattening phase can be performed in Arapaima gigas. [ABSTRACT FROM AUTHOR]

Fish viscera can be an important source of protein and energy for aquafeed, and its use contributes to circular aquaculture. The aim of this study was to produce acid and fermented silage from fish viscera to determine their nutritional value and the apparent digestibility coefficient of nutrients and energy for juvenile tambaqui (Colossoma macropomum). An acid silage and three fermented silages with different sources of carbohydrates (molasses, wheat bran, and cassava waste) were produced with 0.25% sorbic acid as an antifungal in the formulation. Silages presented an average of 55% dry matter, 62.9% lipids, and 12% crude protein. Leucine and lysine predominated as essential amino acids in the acid silage and fermented silages. Fish viscera silages presented EPA and DHA content from 5.4 to 17.8 and 1.7 to 8.9 mg.g−1 of lipids, respectively. The apparent digestibility coefficient (ADC) (indirect method) was above 82% for gross energy for all the formulations. The ADCs for protein were similar for the fermented silages, with a maximum 92% level for the fermented wheat bran silage. The bioconversion of fish viscera into silage makes it an energy ingredient for aquafeed that is well digested by tambaqui juveniles.

Tambaqui or cachama (Colossoma macropomum) is one of the most important neotropical freshwater fish used for aquaculture in South America, and its production is concentrated at low latitudes (close to the Equator, 0°), where the water temperature is warm. Therefore, understanding how selection shapes genetic variations and structure in farmed populations is of paramount importance in evolutionary biology. High‐throughput sequencing to generate genome‐wide data for fish species allows for elucidating the genomic basis of adaptation to local or farmed conditions and uncovering genes that control the phenotypes of interest. The present study aimed to detect genomic selection signatures and analyze the genetic variability in farmed populations of tambaqui in South America using single‐nucleotide polymorphism (SNP) markers obtained with double‐digest restriction site‐associated DNA sequencing. Initially, 199 samples of tambaqui farmed populations from different locations (located in Brazil, Colombia, and Peru), a wild population (Amazon River, Brazil), and the base population of a breeding program (Aquaculture Center, CAUNESP, Jaboticabal, SP, Brazil) were genotyped. Observed and expected heterozygosity was 0.231–0.350 and 0.288–0.360, respectively. Significant genetic differentiation was observed using global FST analyses of SNP loci (FST = 0.064, p < 0.050). Farmed populations from Colombia and Peru that differentiated from the Brazilian populations formed distinct groups. Several regions, particularly those harboring the genes of significance to aquaculture, were identified to be under positive selection, suggesting local adaptation to stress under different farming conditions and management practices. Studies aimed at improving the knowledge of genomics of tambaqui farmed populations are essential for aquaculture to gain deeper insights into the evolutionary history of these fish and provide resources for the establishment of breeding programs. [ABSTRACT FROM AUTHOR]

River damming threatens freshwater biodiversity worldwide by isolating populations, reducing both gene flow and genetic variation, and affecting the ability of a given population to adapt to environmental changes.Herein, we employed a microsatellite DNA marker panel and a multitemporal approach to assess the effects of damming on the genetic diversity of a long‐lived species from both contemporary and historical perspectives. To accomplish this, we used the migratory catfish Pseudoplatystoma corruscans as a model and sampled it in two South American basins. We tested whether: (1) populations from dammed and undammed environments would display different levels of genetic diversity; (2) ecosystem size would influence the level of genetic diversity; and (3) projected whether fish populations would maintain their current genetic diversity in the long term.Our findings reveal that P. corruscans populations from dammed landscapes with smaller ecosystems showed smaller estimated effective population size, lower genetic diversity, and higher relatedness coefficient than in intermediate ecosystem size in both dammed and undammed environments. We also noticed changes in estimated gene flow and effective population size from both contemporary and historical perspectives, probably because of dams. Predictive genetic diversity analysis revealed a critical scenario for the long‐term persistence of P. corruscans in dammed environments with smaller ecosystem sizes.Our study suggests that anthropogenic barriers have substantially impacted genetic diversity and genetic structuring of the migratory fish P. corruscans. Thus, the formation of conservation policies is urgently needed to avoid local extinctions of this species in fragmented riverscapes. We highlighted the effectiveness of large ecosystems and connectivity between populations in conserving genetic diversity of migratory fishes. [ABSTRACT FROM AUTHOR]

To promote the maximum fertilization rates (FRs) and normal embryonic development, the appropriate ratio of motile sperm to oocytes and adequate water volume should be applied in fish. Therefore, the aim of this study was to determine the proportion of "sperm: egg: water" for maximum use in artificial fertilization in Brycon insignis. A completely randomized experimental design in a factorial scheme (4 × 4) was applied that consisted of four inseminating doses (50,000, 350,000, 650,000 and 950,000 mobile sperm per oocyte), and they were activated with four different volumes of water (1, 5, 10 and 15 ml g−1 of oocytes), performed in triplicate. There was a significant effect on the FR (p < 0.05; R = 69.5%) and hatching rate (p < 0.05; R = 64.2%) with a linear increasing effect up to 152,172 and 130,870 mobile sperm oocytes−1 ml−1 of water respectively. Furthermore, to fertilization and hatch rates, the significative effects (p < 0.05) were verified on surface response model with lower rates when the large water volume and low sperm quantity were applied. On the other hand, low volumes of water, with low or high sperm doses, produced better results. In other words, large amounts of water can only be applied when associated with high amounts of sperm. For the percentage of normal larvae, there was significant difference (p < 0.05) on surface response model, with higher values to intermediary sperm doses and water volume. Thus, B. insignis reproduction can be optimized if the ratio of semen (0.68 ml): oocytes (100 g): water (100 ml) is applied to the procedure. [ABSTRACT FROM AUTHOR]

Triploidy induction is one of the promising techniques to increase growth in aquaculture and may minimize the negative impacts that escaped fish may present to the environment. The aim of this study was to evaluate the efficiency of cold shocks in producing triploid individuals using a Neotropical migratory fish species, the curimba (Prochilodus argenteus). Cold shocks (4ºC) were applied at different times (5, 10, and 12 min) after fertilization and for varying shock durations (10, 15, 20, and 25 min). Survival rates were not different between triploid and diploid controls at 43 days after hatching, at the end of the juvenile stage. The best parameters for triploidy induction were cold shock (4°C), applied 5 min after fertilization for 25 min, resulting in 100% triploid fish. This triploidy induction protocol is simple and can be used in widespread aquaculture productions. [ABSTRACT FROM AUTHOR]

The cryopreservation process causes damage to sperm structures and supplementation of the cryoprotective medium is an alternative to reduce these damages. The aim of this study was to determine the effect of melatonin supplementation on post-thaw sperm quality in Prochilodus lineatus. The cryoprotective medium was supplemented with 2.00, 2.75, 3.50, and 4.25 mM melatonin, and the control group (without melatonin). Sperm motility parameters, membrane integrity, sperm morphology, oxidative stress (lipid peroxidation and enzymatic activity), and fertilization capacity were analyzed in the post-thaw sperm. Samples cryopreserved with 2.00 mM melatonin yielded higher sperm motility rate than other treatments with the addition of melatonin. Sperm curvilinear velocity (VCL) and average path velocity (VAP) were higher in samples containing 2.00 mM melatonin than in other treatments. Samples from control and with 2.00 mM melatonin presented higher membrane integrity and morphological normality than samples containing 4.25 and 2.75 mM melatonin, respectively. Regarding oxidative stress, lower lipid peroxidation (LPO) occurred in 2.75 and 3.50 mM melatonin, compared to control. While higher enzyme activity of catalase (CAT) occurred in the control than in other treatments, no differences were observed in the activity of superoxide dismutase (SOD). Higher fertilization and hatching rates occurred at 2.75 mM melatonin compared to 4.25 mM. Although no significant differences were observed in LPO between the control and samples supplemented with 2 mM melatonin, it was observed that this dosage of melatonin allowed higher VCL and VSL and reduced values of CAT. However, as there are no differences in motility and fertilization rates between the control and the 2 mM concentration, it is suggested that further studies be carried out with lower concentrations of melatonin in order to determine its effectiveness as an antioxidant in the sperm of this species. • 2 mM melatonin increase curvilinear and average path velocities in post-thaw sperm in Prochilodus lineatus. • 2–4.25 mM melatonin supplementation reduces catalase enzyme activity in post-thaw sperm. • High melatonin concentration (4.25 mM) negatively affect post-thaw sperm quality. [ABSTRACT FROM AUTHOR]

Systematic review and meta-analysis (MA) were performed to summarize scientific evidence of the effects of cryopreservation of sperm from South American species of freshwater fish using the motility rate as an indicator. The search strategy was applied to four electronic databases, and the inclusion criteria were studies conducted on neotropical fish, including semen, that were submitted to cryopreservation. Meta-analysis for random effects was performed for each indicator according to the general average of fresh (control) and cryopreserved (treated) semen. A total of 25 publications reporting 26 studies and 116 trials were included in the MA. Heterogeneity was observed between studies for all variables. In general, cryopreserved semen showed lower advanced motility, an increase of which was observed (P < 0.01) in a greater proportion of semen dilution. Results showed that cryopreservation with the use of cryoprotectants such as alcohols and amides seem to favor the motility rates of the cryopreserved semen of neotropical South American freshwater species. [ABSTRACT FROM AUTHOR]